Atheists and naturalists are critical of Christians for their beliefs. Belief in gods and demons is, for them, and indication of being influenced by mythology and not paying attention to new evidence from science.
Such a disposition against belief in gods or demons is found in the title of Carl Sagan's book "The Demon Haunted World."
But are we really that foolish for believing in demons? Some atheists are at least open to aliens or life on other planets. Let's compare traditional beliefs about aliens (in culture) with traditional beliefs about demons.
Traditional Characteristics of Aliens and Demons
Both demons and aliens are:
1) non-human persons
2) Capable of inter-dimensional travel
3) Are hostile to humans
4) Can change form
5) Can read minds
6) Have religious practices surrounding them (UFO cults, witchcraft)
7) Appear humanoid and frightening
Evidence for Aliens vs. Demons
I actually have more evidence for demons than for aliens of this type. The principle evidence of aliens surrounds 1) UFO sightings and 2) alien abduction reports. UFO sightings aren't really evidence of aliens in the traditional sense, because no is actually seeing "little green men" who are performing the characteristics listed above. However, alien abduction reports would work as evidence.
However, I don't know anyone who has been abducted by aliens. I know at least 2 people who have seen a demon in unexpected circumstances, and became extremely distraught by it. (Where talking like physically seeing it or it talking to them). I am not even sure if one of them is a religious person. I also have read a book where the author mentioned seeing a very frightening face of a demon while laying in his bed (the book wasn't about demons, but about something related to Christian life or something).
Aliens and Demons: Is There a Major Difference?
This is not to say that all or even any of these reports should be believed (about aliens or demons). But it shows that a belief in demons is more rational than belief in aliens if we base the evidence solely on observation. I have more independent testimony of the observation of demons than of aliens. But this is only if we can actually differentiate between the two based on appearance.
Someone may retort that the universe is so big that life had to evolve elsewhere. But this says nothing about the qualities of this life. If I was to meet an alien that met the traditional criteria I list above, I would have no reason to assign the title "alien" or "demon" to it. In fact, I would not know of any actual difference between the two. If I met some creatures of this nature, it may as well be a demon.
Someone may reply and say well demons used to be in the presence of God, but rebelled, whereas aliens didn't. But how would I know if the "aliens" were unaware of God? If the aliens are hostile to humans, for all I know, they know about God and hate him too. Someone may say that demons are "non-physical" whereas aliens are "physical." But there is no basis in the Bible for such a distinction. There is a basis for saying that angels/demons can do violent and physical things and change form- just like an "alien."
Someone may reply and say that on this standard, how do I know that the demon appearances are actually demons and not "aliens" instead? I don't. If I saw something that looked like an "alien," I could just as easily say the demon is changing its form to deceive us of its origin.
There is simply precious little practical difference between "aliens" and "demons" as traditionally understood.
On another note, this is why its unreasonable to have your faith affected by the discovery of "extraterrestrial life".
What Difference Does It Make?
None of this is at all intended to provide evidence for aliens or demons. But if you are open to aliens, but closed to demons, you may have to rethink how consistent you are being.